Bottom corners curl up during printing (warping?)

[jeex]

Hello,

I use the Ultimaker2 which has a heated glass plate at 60 degrees celsius (140 Fahrenheit) as standard setting. As you can see in the image the bottom corners curl up slightly despite the brim i use. Even the brim is pulled up by the object. The filament is PLA.

556b24282e838.JPG

As the object is on the plate for many hours, i think it shrinks like loundry that is overheated. So first question: how can i tell gcode to lower the temp of the glassplate after say 5mm. The object then is heavy enough by itself not to move around. And i can put some "glue" under the object to fixate it.

Or is there another reason why this happens?

Thanks.

[curious aardvark]

try slowing down the first layer print speed. And I mean REALLY slow. I run mine at 10% of print speed and usually print at between 50 - 70mms.
That way you get an awful lot more adhesion to the print bed.

If that doesn't work - wipe the bed with a gluestick.
But be warned - slow first layer and glue stick can be almost impossible to remove :-)

[jeex]

Thanks.

Board is ready. Beautiful result. But measuring shows that the first centimeter has shrunk over all by 10% and some more on the edges where it curls up.

What i'll do now is
- print it laying down in stead of standing up (the board is 130x105x25).
- print the first layers with brim very slow (thanks for the advice).
- Then after 5mm i lower the temp of the glass plate to 30 degrees C.

Any more suggestions?

[curious aardvark]

don't lower the bed temp. The longer the plastic stays soft, the flatter the base will be.
Cooling the bed just encourages the plastic to shrink.
So keep it at 60 for the whole print.

10% ? shrinkage, with pla ?
That's just wrong, hell even abs only shrinks by 1%. What pla are you using ?

[jeex]

10% in the corners. I put a small square in each corner and the ones in the bottom corners are rectangles by now. See images. It should have been flat with a small fillet. The one on the left is empty on the inside, the one in the right has a 15% fill but still curls op on the corner. On a third attempt even the brim curled up.

556999bbd2434.JPG

[Marm]

Wait.... you're not using an adhesive?

[jeex]

Wait.... you're not using an adhesive?

The UM2 has a heated bed. For smaller things adhesive was not necessary. Now 'll put some glue on the glass. I'll be back with the results.

[Marm]

Yeah, Even with a heated bed, I ALWAYS use glue. Check one of the thousand threads we have here on bed adhesion for tips.

[jeex]

Used a household glue stick and that helped.

[wenganxiang]

You can smear a layer of glue on glass to make the filament stick to it.